Green steam industrial steam generator process and system

ABSTRACT

A steam generation system includes a silo, a heater, a material transfer system, and a heat exchanger. The silo is configured to receive granular material into the silo at an upper portion of the silo. The heater is arranged at or in the upper portion of the silo to heat the granular material received into the silo. The material transfer system is arranged to remove granular material exiting from a bottom of the silo. The heat exchanger is disposed in a lower portion of the silo and is arranged to contact granular material flowing downward inside the silo. The electricity for operating the heater may be generated by a renewable energy source such as a solar energy source or a wind energy source.

This application claims the benefit of U.S. Provisional Application No.63/358,076 filed Jul. 1, 2022. U.S. Provisional Application No.63/358,076 filed Jul. 1, 2022 is incorporated herein by reference in itsentirety

BACKGROUND

The following relates to the green energy arts, steam generation arts,and related arts.

BRIEF SUMMARY

In some illustrative embodiments disclosed herein as nonlimitingexamples, a steam generation system includes a silo, a heater, amaterial transfer system, and a heat exchanger. The silo is configuredto receive granular material into the silo at an upper portion of thesilo. The heater is arranged at or in the upper portion of the silo toheat the granular material received into the silo. The material transfersystem is arranged to remove granular material exiting from a bottom ofthe silo. The heat exchanger is disposed in a lower portion of the siloand is arranged to contact granular material flowing downward inside thesilo.

In some illustrative embodiments disclosed herein as nonlimitingexamples, a steam generation method is disclosed which is performed inconjunction with the steam generation system of the immediatelypreceding paragraph. The steam generation method includes: deliveringgranular material to the upper portion of the silo of the steamgeneration system; delivering electricity to operate the heater of thesteam generation system; and flowing a heat transfer fluid through theheat exchanger of the steam generation system. In some embodiments, thedelivering of the granular material, the delivering of the electricity,and the flowing of the heat transfer fluid are performed concurrently.In some embodiments, the delivering of the electricity to operate theheater comprises generating the electricity from solar energy or fromwind energy.

In some illustrative embodiments disclosed herein as nonlimitingexamples, a steam generation system includes a silo, a heater, a heatexchanger, a material transfer system, and a storage silo. The silo isconfigured to receive granular material into the silo at an upperportion of the silo. The heater is arranged to heat the receivedgranular material to generate heated granular material. The heatexchanger is disposed in a lower portion of the silo and is arranged toextract heat from the heated granular material flowing downward in thesilo to generate cooled granular material. The material transfer systemis arranged to remove the cooled granular material exiting from a bottomof the silo. The storage silo is connected to store the cooled granularmaterial removed by the material transfer system and to transfergranular material from the storage silo to the upper portion of thesilo.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 diagrammatically illustrates a green steam system for superheatedsteam production.

FIG. 2 diagrammatically illustrates a more detailed view of the heatexchanger modules of the illustrative green steam system of FIG. 1 .

FIG. 3 diagrammatically illustrates suitable water/steam circuit of thesystem of FIGS. 1 and 2 .

DETAILED DESCRIPTION OF THE INVENTION

Steam generation systems and methods disclosed herein provide eithersaturated or superheated steam for industrial process use from renewableenergy sources such as solar and wind. Hence, such steam generationsystems are also referred to herein as green steam systems. Solidparticles are used to absorb and store energy from the availablerenewable sources. When steam is needed, energy is transferred from thesolid particles to a heat transfer fluid in a suitably designed heatexchanger. In embodiments in which the heat transfer fluid is water,steam is generated directly and sent to the industrial process. Inembodiments in which the heat transfer fluid is not water, a second heatexchanger is suitably used to generate steam from the hot heat transferfluid. The green steam system is flexible and can be configured withdifferent heat transfer surfaces for different applications. Anonlimiting illustrative example configuration for producing superheatedprocess steam is described in the following.

With reference to FIG. 1 , an illustrative green steam system is shown.Also shown in FIG. 1 are an industrial facility F operatively connectedwith the illustrative green steam system, and grade level G is alsoindicated with an illustrative truck T disposed thereon. In this system,sand or other granular material is passed by gravity through an electricheater 10 where the temperature of the particles is raised to (in onenonlimiting illustrative embodiment) between 600° C. (1112° F.) and 650°C. (1202° F.). The temperature the granular material is heated to iscontrolled by the rate at which the granular material is delivered andthe electricity delivered to the heater 10 (i.e., how hot the heater 10is run). In some embodiments these parameters are set to ensure thegranular material is heated to a temperature of at least 600° C.

The electric heater 10 operates on renewable energy and is located abovean insulated silo 12 where the hot sand is stored. Hence, the insulatedsilo 12 is also referred to herein as a hot silo 12 or hot sand silo 12.The illustrative heater 10 is disposed above the silo 12, between ahopper 14 and a top 12 _(T) of the silo 12; however, it is alsocontemplated for the heater to be integrated into an upper portion ofthe silo. The electricity for operating the electric heater 10 may, byway of nonlimiting illustrative example, be generated by a renewableenergy source such as electricity from solar energy generated byphotovoltaic solar panels, solar thermal collectors, concentrated solarpower systems, or so forth; electricity from wind energy produced by awind turbine farm or the like; or another type of renewable energy. Thehot sand particles exit a bottom 12 _(B) of the silo 12 and flow underthe force of gravity through multiple heat exchanger modules 20, 22, 24,26 where the sand transfers its energy to the water and steam. The sandexits the heat exchangers modules 20, 22, 24, 26 as cold sand at (in onenonlimiting illustrative embodiment) a temperature between 150° C. (302°F.) and 200° C. (392° F.) and is conveyed to a bucket elevator or othersand transfer system 30 which lifts the cold sand to a top 40 _(T) of asecond insulated silo 40, also referred to herein as a cold sand silo 40or cold silo 40, or as a storage silo 40. In the illustrative example,the sand transfer system 30 lifts the cold sand to a hopper 42 at thetop 40 _(T) of the second insulated silo 40. The delivering of thegranular material and the delivering of the electricity and the flowingof the heat transfer fluid can be adjusted to cool the granular materialexiting from the bottom 12 _(B) of the hot silo 12 to a temperature of200° C. or lower in some embodiments. When renewable energy is availablefor the electric heater 10, the sand is removed from a bottom 40 _(B) ofthe second (i.e., storage) silo 40 by a screw conveyor or other sandtransfer system and is fed to a bucket elevator or other sand transfersystem 44 which lifts the sand to the inlet of the electric heater 10(e.g., the sand is delivered by the sand transfer system 44 to thehopper 14 located above the heater 10 in the illustrative example ofFIG. 1 ).

With reference to FIG. 2 , a more detailed view of the heat exchangermodules 20, 22, 24, 26 of the illustrative green steam system of FIG. 1is shown. The illustrative heat exchanger modules are arranged in twoparallel particle flow paths P1 and P2. Particle flow path P1 is alsoreferred to herein as sand flow path #1; and similarly particle flowpath P2 is also referred to herein as sand flow path #2. Each particleflow path P1, P2 contains two heat exchanger modules arranged in aseries configuration. In the first flow path P1 (“Sand flow path #1),the sand passes through a generating bank module 20 for producingsaturated steam and then through an economizer module 22 for heating thefeed water to near saturation. In the second flow path P2 (“Sand flowpath #2), the sand passes through a superheater module 24 for producingsuperheated steam and then through a second economizer module 26 forheating the feed water to near saturation. During operation, all heatexchanger modules 20, 22, 24, and 26 are full of slow moving, looselypacked sand particles.

The generating bank module 20 and the superheater module 24 are designedwith heat exchanger tubes oriented vertically, as diagrammatically shownin FIG. 2 , parallel to the sand flow direction (i.e., parallel withflow paths P1 and P2). This advantageously reduces the flow resistanceto the sand presented by the heat exchanger tubes of the generating bankmodule 20 and the superheater module 24. The heat exchanger tubes of thegenerating bank module 20 are connected to an inlet header 20 _(In) atthe bottom of the generating bank module 20 and an outlet header 20_(Out) at the top of the generating bank module 20. Likewise, the heatexchanger tubes of the superheater module 24 are connected to an inletheader 24 _(In) at the bottom of the superheater module 24 and an outletheader 24 _(Out) at the top of the superheater module 24. This providesa flow of water/steam which is countercurrent to the sand flow (i.e.,countercurrent to the direction of the sand flow paths P1 and P2). Thiscounterflow arrangement advantageously maximizes heat transfer from thehot sand to the water/steam. The headers 20 _(In), 20 _(Out), 24 _(In),24 _(Out) as well as the connecting tubes are suitably covered with arefractory material to protect them from erosion caused by the sandflow. The heat transfer tubes are arranged in a staggered bundle. Flowdisruptors are optionally attached to each tube in a pattern so as tomove cold sand away from the outer tube wall and move hot sand towardthe outer tube wall. The optional flow disruptors cover the entiresurface of each tube and can be a pin stud design or a fin design, astwo nonlimiting examples.

In some nonlimiting illustrative embodiments, the economizer modules 22and 26 are designed with heat exchanger tubes oriented horizontally, asdiagrammatically shown in FIG. 2 , and parallel to the long axis of themodule. The tubes are connected in a serpentine manner with tubesconnecting to tubes at the next higher elevation using a “U” bends. Thetubes are arranged in a staggered bundle as viewed from the ends of thetubes. The staggered bundle assists in keeping the sand mixed, so thetubes see a more uniform sand temperature. The tubes are connected to aninlet header at the bottom of the module and an outlet header at the topof the module (not shown in FIG. 2 ). This provides an overall waterflow which is counter to the sand flow even though each individual tubeis in cross flow.

In the illustrative embodiment, the bottom of each economizer module 22and 26 includes screw conveyors 50 oriented parallel to the long axis ofthe economizer module. The screw conveyors 50 are adjacent to each otherwith no gaps in between. The screw conveyors 50 control the flow of sandthrough the heat exchanger modules 20, 22, 24, 26 by removing sand fromthe bottom of the economizer modules 22, 26 and transporting it to theinlet (e.g., hopper 42) of the cold silo bucket elevator 30 (see FIG. 1). Because there are multiple screw conveyors 50, the sand flow invertical lanes corresponding to the respective screw conveyors 50 can beadjusted independently to account for uneven sand temperaturedistributions or flow imbalances in the heat exchangers 20, 22, 24, 26.While mutually parallel screw conveyors 50 are illustrated, inalternative embodiments other types of sand transport are contemplated,such as a bank of mutually parallel conveyor belts orientedperpendicular to the long axis of the economizer modules 22 and 26.

FIG. 2 shows a vertical channel 52, referred to herein as a silo drain52, located below the centerline of the hot silo 12 in between the heatexchanger modules 20, 22 of the first particle flow path P1 and the heatexchanger modules 24, 26 of the second particle flow path P2. Thisvertical channel 52 provides a sand flow path P3 that feeds one (asshown, or optionally more) of the screw conveyors 50. The silo drain 52is used to remove sand from the hot silo 12 during maintenanceactivities, during extended shutdowns, or in the event of a situationcalling for rapid removal of the hot sand. The screw conveyors 50 arewater cooled and transport the sand to the inlet of the cold silo bucketelevator 30 (see FIG. 1 ). Under normal operating conditions, the drain52 is full of non-moving sand.

With reference to FIG. 3 , a water/steam circuit suitably employed inthe illustrative green steam system of FIGS. 1 and 2 is shown. Warmcondensate is returned via a pipe or the like 60 from the industrialprocess (e.g., the illustrative industrial facility F shown in FIG. 1 )and is mixed with fresh makeup water delivered via a water line 61, andthe mixture is delivered via a pipe or the like 62 to the inlet of afeed pump 64 (also indicated in FIG. 1 ). The high-pressure waterdownstream of the feed pump is split into parallel streams 66 and 68which are sent through the two economizer modules 22 and 26 (e.g.,economizer banks #1 and #2 of FIG. 2 ). Nearly saturated water exits theeconomizer modules 22 and 26 and is sent via a riser 69 to a steamseparator 70 (also indicated in FIG. 1 ), which in the illustrativeexample is a vertical separator 70. Water exits a bottom 70 _(B) of thevertical separator 70 and travels through downcomers 71 to the inletheader 20 _(in) of the generating bank module 20. A saturatedsteam/water mix exits the generating bank module 20 at the outlet header20 _(out) and returns through risers 72 to the vertical separator 70.This sets up a natural circulation loop where the flow is driven bydensity differences between the separator 70 and the generating bank 20.The vertical separator 70 also has a blowdown line 76 where water can beremoved from the system to control the buildup of dissolved solidswithin the system. In the illustrative embodiment, the verticalseparator 70 is used instead of a steam drum because the verticalseparator 70 has a better form factor for the green steam application(e.g., it can be conveniently mounted on the hot silo 12 asdiagrammatically shown in FIG. 1 ) and because the vertical separator 70responds more quickly to changes in steam demand. However, it iscontemplated to substitute a steam drum or the like for the illustrativevertical separator 70.

Saturated steam exits the top 70 _(T) of the vertical separator 70 andgoes through a pipe or the like 78 to a steam accumulator 80 (alsoindicated in FIG. 1 ) before going through the superheater module 24, byflowing into the inlet header 24 _(In) of the superheater module 24. Thesuperheated steam exiting the outlet header 24 _(Out) of the superheatermodule 24 is sent via a pipe or the like 82 to the industrial process F(labeled “Steam to process” in FIG. 3 ). The steam accumulator 80 isused in the illustrative green steam system to provide a more rapidresponse to a change in steam demand than changing the sand flow canachieve. Excess steam is stored in the accumulator 80 when the systemproduces more steam than is utilized by the industrial process F. Thestored steam can later be released to meet a rapid increase in steamdemand or to cover some gaps in the availability of the renewable energysource.

The green steam system can also be configured to deliver saturated steaminstead of superheated steam by using a second generating bank moduleinstead of the superheater module 24.

The heat exchanger modules 20, 22, 24, 26 may in some embodiments beself-contained devices which can be disconnected from the system andremoved via a monorail system for maintenance or replacement.

The illustrative heat exchanger modules are arranged in two particleflow paths. However, more than two sands paths are also contemplated foruse in the green steam system.

The illustrative examples employ sand as the granular material. Sand isadvantageously low cost, with high heat capacity and good flowability.However, other granular materials are contemplated for use in the greensteam system, such as gravel, crushed stone, synthetic granularmaterials, or so forth.

While the above description constitutes the preferred embodiment of thepresent invention, it will be appreciated that the invention issusceptible to modification, variation and change without departing fromthe proper scope and fair meaning of the accompanying claims.

1. A steam generation system comprising: a silo configured to receivegranular material into the silo at an upper portion of the silo; aheater arranged at or in the upper portion of the silo to heat thegranular material received into the silo; a material transfer systemarranged to remove granular material exiting from a bottom of the silo;and a heat exchanger disposed in a lower portion of the silo andarranged to contact granular material flowing downward inside the silo.2. The steam generation system of claim 1 wherein the heat exchangercomprises at least one bank of steam-generating tubes.
 3. The steamgeneration system of claim 2 wherein the steam-generating tubes of theat least one bank of steam-generating tubes are oriented vertically. 4.The steam generation system of claim 3 wherein the heat exchangerfurther includes at least one economizer disposed beneath the at leastone bank of steam-generating tubes.
 5. The steam generation system ofclaim 4 wherein the tubes of the at least one economizer arehorizontally and the material transfer system comprises a plurality ofmutually parallel screw conveyors or conveyor belts arranged parallelwith the horizontal tubes of the at least one economizer.
 6. The steamgeneration system of claim 2 further comprising: a steam separator orsteam drum operatively connected with the at least one bank ofsteam-generating tubes.
 7. The steam generation system of claim 6wherein the heat exchanger further includes: a superheater connected toreceive water or steam from the steam separator or steam drum.
 8. Thesteam generation system of claim 7 further comprising: a steamaccumulator interposed between the steam separator or steam drum and thesuperheater.
 9. The steam generation system of claim 1 furthercomprising: a storage silo connected to receive granular materialremoved from the silo by the material transfer system at an upperportion of the storage silo, and to transfer granular material from thestorage silo to the upper portion of the silo.
 10. A steam generationmethod comprising: providing a steam generation system including a siloconfigured to receive granular material into the silo at an upperportion of the silo, a heater arranged at or in the upper portion of thesilo to heat the granular material received into the silo, a materialtransfer system arranged to remove granular material exiting from abottom of the silo, and a heat exchanger disposed in a lower portion ofthe silo and arranged to contact granular material flowing downwardinside the silo; delivering granular material to the upper portion ofthe silo of the steam generation system; delivering electricity tooperate the heater of the steam generation system; and flowing a heattransfer fluid through the heat exchanger of the steam generationsystem.
 11. The steam generation method of claim 10 wherein thedelivering of the granular material, the delivering of the electricity,and the flowing of the heat transfer fluid are performed concurrently.12. The steam generation method of claim 10 wherein the deliveredgranular material comprises sand.
 13. The steam generation method ofclaim 10 wherein the delivering of the electricity to operate the heatercomprises generating the electricity from solar energy or from windenergy.
 14. The steam generation method of claim 10 wherein thedelivering of the granular material and the delivering of theelectricity is effective to heat the granular material to a temperatureof at least 600° C.
 15. The steam generation method of claim 10 whereinthe delivering of the granular material and the delivering of theelectricity and the flowing of the heat transfer fluid is effective tocool the granular material exiting from the bottom of the silo to atemperature of 200° C. or lower.
 16. A steam generation systemcomprising: a silo configured to receive granular material into the siloat an upper portion of the silo; a heater arranged to heat the receivedgranular material to generate heated granular material; a heat exchangerdisposed in a lower portion of the silo and arranged to extract heatfrom the heated granular material flowing downward in the silo togenerate cooled granular material; a material transfer system arrangedto remove the cooled granular material exiting from a bottom of thesilo; and a storage silo connected to store the cooled granular materialremoved by the material transfer system and to transfer granularmaterial from the storage silo to the upper portion of the silo.
 17. Thesteam generation system of claim 16 wherein the heat exchanger comprisesat least one bank of vertically-oriented steam-generating tubes.
 18. Thesteam generation system of claim 17 wherein the heat exchanger furtherincludes at least one economizer comprising horizontally-oriented tubesdisposed beneath the at least one bank of steam-generating tubes. 19.The steam generation system of claim 18 wherein the material transfersystem comprises a plurality of mutually parallel screw conveyors orconveyor belts arranged parallel with the horizontally-oriented tubes ofthe at least one economizer.
 20. The steam generation system of claim 16further comprising: a steam separator or steam drum operativelyconnected with the at least one bank of steam-generating tubes; and asteam accumulator connected to accumulate steam output by the steamseparator or steam drum; wherein the heat exchanger further includes asuperheater connected to receive steam from the steam accumulator.